Medical articles are frequently used for delivery of therapeutic agents. For example, an implantable or insertable medical device, such as a stent or a catheter, may be provided with a polymer matrix coating layer that contains a therapeutic agent. Upon placement of the medical device at a desired location within a patient, the therapeutic agent is released from the polymer matrix and into the patient, thereby achieving a desired therapeutic outcome.
Such coatings, however, are frequently formed from relatively soft and tacky polymers, which may experience damage, for example, due to the mechanical forces that are exerted upon the medical device during loading and deployment of the same. In addition, where stents are utilized, unwanted polymer bridges can be created over the stent windows during stent deployment. Furthermore, where a biostable polymer is utilized as a coating material, an empty polymer shell remains after the drug has been eluted, which may be disadvantageous in some instances.
In contrast to most polymers used in for drug delivery, metallic structures (e.g., stainless steel and nitinol) and ceramic structures (e.g., aluminum oxide, titanium oxide and iridium oxide) are quite robust, resulting in excellent resistance against mechanical damage. Moreover, metallic and ceramic structures are frequently more biologically inert than polymers, and in some cases are biocompatible. Furthermore, metallic and ceramic structures can be made porous, thereby enabling them to hold large amounts of drugs. Unfortunately, drug release from porous structures is typically not well controlled.
The above and other challenges are addressed by the present invention.